Seamed press felt of multilayered base-fabric structure for papermaking and process for producing the same

ABSTRACT

A single-seam felt which employs a base fabric of a multilayer structure and which, despite this, is excellent in wet-web surface smoothness and has satisfactory batt adhesion. It is free from wrap protrusion and weft fraying in the seamed part of the layered base fabric.

FIELD OF THE INVENTION

The present invention relates to a seamed papermaking press felt with a multilayer base fabric structure, which is a felt used in a press part of a papermaking machine, and a method for producing the same.

PRIOR ART

In recent years, as a result of the increase in operating speed so as to improve productivity, felts with a base fabric of a thick and hard multilayer structure have come to be used in the press part of papermaking machines. This improves wear resistance and dewatering capability during high speed operation and facilitate the installing operations onto the papermaking machine by means of an open-ended type constitution in which seams are formed at both end edges of the base fabric.

Conventional seamed felts, which have seam loops at both ends, are made into an endless form by interdigitating said seam loops with one another after passing them between the rolls of the papermaking machine and joining them by passing a pintle wire through the common hole thus formed. Due to adopting a multilayer structure base fabric it is possible to obtain high quality seamed felts of a greater void volume than with seamed felts of a single base fabric, which are suitable for parts with high dewatering volume and parts with high nip pressure.

This type of seamed felt is made into an open-ended form by joining a base fabric having seam loops into an endless form via a pintle wire passed through the seam loops, by using this as a lower fabric on the external circumference of which one or more layers of an upper fabric made from a base fabric without seam loops is (are) superposed, by attaching the upper fabric with the lower fabric by needling after posing a batt material on the external circumference of the upper fabric, and by thereafter cutting the upper fabric in the widthwise direction at the seam loop part of the lower fabric or in the vicinity thereof.

However, when cutting the upper fabric in the widthwise direction, there is the problem that the warp yarns constituting the base fabric will fray at the cut part and that the weft yarns of the upper fabric will come loose at the end parts. Such frayed or loose yarns in the felt surface have a negative effect on the quality and operability of paper since they can cause markings and holes in the wet paper; there are even cases in which the paper is ruptured.

In order to solve the above-mentioned problems, measures for preventing the fraying or loosening of yarns at the cut part of the cut upper fabric have been devised in the prior art.

In patent documents 1 and 2, heat melt fibers of a low melting point material are used for the yarns constituting the upper fabric, and the crossing points are stuck to each other (refer to patent document 1, FIG. 5). Moreover, the use, in the lowest layer of the base fabric (the opposite side of the wet paper), of a greater number of weft yarns than of warp yarns (patent document 3), the formation of an area without weft yarns in the cut part (patent document 4), the use of multiple layers (at least two layers) in a base fabric having seam loops in which, by offsetting the seam part, the base fabric (i.e., the weft yarns) is not cut (patent document 5), and other technologies have been proposed.

Even though it is possible to obtain the effect of preventing the yarns from fraying and loosening by these means to some extent, only insufficient effect is achieved under severe conditions. With the technology according to patent documents 2 through 4, which cannot withstand the severe conditions of the repeated compression occurring in the press part of a papermaking machine and the changes in tension before and after pressing, the base fabric tissue will come loose at the cut part. With the technology according to patent document 5, in which there is an area without weft yarns, there is further problems that the adhesion of the batt in this area is bad and that fiber loss and wear of the felt in this area will be accelerated.

With the technology according to patent document 5, seam loops are also formed in the base fabric on the wet paper contacting side. Yarns need to have sufficient strength to form seam loops, which means that yarns of a big diameter have to be used; however, base fabrics woven with yarns of a big diameter have a rough surface, which causes the wet paper to have a bad surface smoothness, and since the adhesion of the batt is also bad, fibers are easily lost and the felt is quickly worn. Moreover, due to a plurality of seam parts, only inferior seaming operations during installation are achieved.

-   [Patent Document 1] JP, A, 11-100787 -   [Patent Document 2] JP, A, 2003-96685 -   [Patent Document 3] U.S. Pat. No. 4,863,786 -   [Patent Document 4] JP, A, 2004-36020 -   [Patent Document 5] Canadian Patent 2229121

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The object of the present invention, after reflecting upon the above-mentioned problems, in particular the use of felts using a base fabric of a thick and hard multilayer structure that resulted from the increase in operating speed, is to provide a single seam felt, for excellent surface smoothness of the wet paper, having good adhesion to the batt, and wherein, at the seam part of the stacked base fabric, the warp yarns do not fray and the weft yarns do not come loose.

Means for Solving the Problems

The present invention essentially relates to a seamed papermaking press felt with a multilayer base fabric structure and is based on the technologies hereinafter.

(1) Seamed papermaking press felt comprising a woven base material having seam loops at both ends and a batt layer, wherein

said base material comprises a first base fabric having seam loops at both ends which is joined into an endless form by passing a pintle wire through said seam loops and one or more second base fabric(s) having seam loops at both ends, through which a pintle wire is not passed, which is (are) stacked onto said first base fabric,

said batt layer, which is disposed at least on the wet paper side of said base material and is entangled with said base material, is cut in the widthwise direction in the vicinity of the seam loop part of said second base fabric.

(2) Seamed papermaking press felt wherein the weight per area unit of said second base fabric is lower than the weight per area unit of said first base fabric. (3) Seamed papermaking press felt wherein the opening formed by the seam loops of said second base fabric is smaller than the opening formed by the seam loops of said first base fabric. (4) Seamed papermaking press felt wherein the loop length and loop height of the seam loops of said second basic fabric are respectively smaller than the loop length and loop height of said first base fabric. (5) Seamed papermaking press felt wherein, in the vicinity of the seam loop part of said second base fabric, yarns are further disposed to reduce the opening formed by the seam loop of said second base fabric. (6) Seamed papermaking press felt wherein said yarns are multi-filaments, bulky yarns or spun yarns. (7) A kit comprising a seamed papermaking press felt, which comprises a woven base material having seam loops at both ends and a batt layer, and only one pintle wire to be passed through the seam loops, wherein

said base material comprises a first base fabric having seam loops at both ends and one or more second base fabric(s) having seam loops at both ends which is (are) stacked onto said first base fabric,

said batt layer, which is attached by entanglement at least to the wet paper side of said base material, is cut in the widthwise direction at the seam loop part of said second base fabric or in the vicinity thereof,

said pintle wire joins said first base fabric into an endless form on the papermaking machine by being passed through the seam loops of said first base fabric.

(8) A method for producing a seamed papermaking press felt comprising a woven base material having seam loops at both ends and a batt layer, comprising

a process for making said base material by stacking one or more second base fabric(s) having seam loops at both ends onto a first base fabric having seam loops at both ends,

a process for making endless forms by joining the seam loops of one end of said first base fabric with the seam loops of the other end via a pintle wire and by joining the seam loops of one end of said second base fabric with the seam loops of the other end via a pintle wire,

a process for entangling a batt layer with said base material by disposing it on the wet paper side of said base material which comprises said first base fabric and said second base fabric which have been made into endless forms,

a process for making open-ended forms of said first base fabric and said second base fabric by withdrawing the pintle wires from the seam loops of both said first base fabric and said second base fabric,

a process for making an open-ended felt by cutting said batt layer in the widthwise direction at the seam loop part of said second base fabric or in the vicinity thereof, and

a process for making an endless form on the papermaking machine by re-inserting a pintle wire only into said first base fabric.

(9) A method for producing a seamed papermaking press felt, further comprising a process for weaving yarns in the vicinity of the seam loop part of said second base fabric, when said second base fabric is woven, to reduce the opening formed by the seam loops of said second base fabric. (10) A method for producing a seamed papermaking press felt, further comprising a process for inserting yarns in the vicinity of the seam loop part of said second base fabric, after weaving the second base fabric and before entangling the batt part with the base material, to reduce the opening formed by the seam loops of said second base fabric.

ADVANTAGES OF THE INVENTION

According to the present invention, it is possible to provide a single seam felt for excellent surface smoothness of the wet paper, having good adhesion to the batt, and wherein, at the seam part of the stacked base fabric, the warp yarns do not fray and the weft yarns do not come loose.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 An enlarged sectional view of a felt according to the present invention at the seam loop part and the vicinity thereof before the felt is cut in the widthwise direction at the seam part or the vicinity thereof.

FIG. 2 An enlarged sectional view of a felt according to the present invention at the seam loop part and the vicinity thereof when the felt is cut in the widthwise direction at the seam part or the vicinity thereof.

FIG. 3 An enlarged sectional view of a felt according to the present invention at the seam loop part and the vicinity thereof after installing on a papermaking machine wherein the felt is cut in the widthwise direction at the seam part or the vicinity thereof.

FIG. 4 A view of a felt according to the present invention in which yarns are disposed in the vicinity of the seam loop part of the second base fabric.

FIG. 5 A view of the prior art.

FIG. 6 A illustrative diagram of a marking test.

FIG. 7 A illustrative diagram of a wear test used for measuring the amount of lost fibers.

EXPLANATION OF THE SYMBOLS

-   1: Felt according to the present invention -   10: First base fabric -   11: Warp yarn of the first base fabric -   12: Weft yarn of the first base fabric -   13: Pintle wire of the first base fabric -   1L: Seam loops of the first base fabric -   1LL: Loop length of seam loops of the first base fabric -   1LH: Loop height of seam loops of the first base fabric -   20: Second base fabric -   21: Warp yarn of the second base fabric -   22: Weft yarn of the second base fabric -   23: Pintle wire of the second base fabric -   2L: Seam loops of the second base fabric -   2LL: Loop length of the second base fabric -   2LH: Loop height of the second base fabric -   30: Batt layer -   40: Cut part

PREFERRED EMBODIMENTS OF THE INVENTION

The fiber materials used for the yarns constituting the base fabrics and for the batt layer in the present invention, which can be those that are generally used for the press felts of papermaking machines, are appropriately be selected from such fiber materials as nylon, polyester, polypropylene, natural materials.

A batt layer is disposed at least on the wet paper side of a base material comprising the first base fabric and one or more second base fabric (s) and is attached to said base material by entanglement with such treatment as needling or fluid entanglement.

Moreover, the present invention is not limited to providing a batt layer only on the wet paper side of the second base fabric; a batt layer can also be disposed on the machine side (roller side) of the first base fabric.

Furthermore, even if the batt layer is disposed only on the wet paper side of the second base fabric, the batt fibers may penetrate to the machine side of the first base fabric when needling is performed.

When a batt layer (batt fibers) is disposed on the machine side of the first base layer, the batt fibers in the vicinity of the seam loops (1L) of the first base fabric may be removed in the widthwise direction.

Moreover, yarns that will swell when the press felt is used may be inserted in the vicinity of the seam loop part of the second base fabric so as to reduce the opening formed by the seam loops of the second base fabric, and to improve the adhesion of the batt and to ameliorate marking. For these yarns, materials with a prescribed moisture percentage of 4.5% or more, e.g. very hydrophilic materials that have the ability to absorb more water content such as nylon, vinylon, acetate, rayon, polynosic, cupra, cotton, hemp, silk, wool, etc. can be used; multi-filaments, bulky yarns and spun yarns made from a tow of 1500 to 1600 dtex are preferably used.

Next, embodiments of the present invention will be explained by referring to the drawings.

FIG. 1 shows felt (1) in the attached state in which a batt layer (30) is entangled with a base material comprising a first base fabric (10) and a second base fabric (20), wherein said batt layer is stacked at least onto the wet paper side of the second base fabric.

This attached felt is produced by abutting the seam loops of the first base fabric having seam loops (1L) at both ends and the second base fabric having seam loops (2L) at both ends so that the respective seam loops interdigitated with one another, by joining said seam loops into endless forms via pintle wires (13), (23) passed through the respective common holes thus formed, and by thereafter entangling both with the batt layer.

After attaching the felt (1) as described above, the pintle wires (13), (23) are once withdrawn and the batt layer (30) is cut in the widthwise direction at the seam loop (2L) part of the second base fabric or in the vicinity thereof (FIG. 2). In this way, the cut part of the batt layer can be formed on the side of wet paper without injuring the seam loops.

By forming the cut part (40) the felt (1) becomes an open-ended form which is joined into an endless form by passing the pintle wire (13) through only the seam loops (1L) of the first base fabric (10) after passing them between the rolls of a papermaking machine. Then, a pintle wire is not inserted into the seam loops (2L) of the second base fabric (20) (FIG. 3). Thus, the felt of the present invention is made up.

Furthermore, by disposing yarns that will swell when the press felt is used in the vicinity of the seam loop part of the second base fabric (20) as weft yarns, it is possible to reduce the opening formed by the seam loops of the second base fabric, improve the adhesion of the batt and ameliorate marking.

The yarns disposed in the vicinity of the seam loop part (outside the seam loops) of the second base fabric can be disposed by weaving yarns different from the fabric when weaving the second base fabric or by inserting into the opening in the vicinity of the seam loop part (outside the seam loops) with a music wire etc. after weaving and before the base material is entangled with the batt part.

The first base fabric and the second base fabric of the present invention are preferably woven fabrics woven with a warp double weave. Furthermore, woven fabrics with a weight per area unit in the range of 300 to 700 g/m², preferably 450 to 650 g/m², for the first base fabric, and 100 to 500 g/m², preferably 200 to 400 g/m², for the second base fabric, can be used as base fabric of the present invention.

Moreover, in the present invention, it is preferred that the opening formed by the seam loops of the first base fabric is 0.24 to 1.86 mm³ per loop and the opening formed by the seam loops of the second base fabric is 0.14 to 0.84 mm³ per loop. It is further preferred in the present invention that the first base fabric has a loop length of 1.50 to 3.00 mm and a loop height of 0.50 to 1.50 mm and that the second base fabric has a loop length of 1.50 to 2.50 mm and a loop height of 0.50 to 1.00 mm. These dimensions can be measured by an optical microscope.

Examples

The seamed papermaking felts of Examples 1, 2 and Comparative Examples 1 through 3 were made by using the fabrics shown in Table 1. The materials used are as follows:

Base fabric material: nylon Batt material: nylon, size 39 dtex Front batt amount: 500 g/m² Back batt amount: 200 g/m² Inserted yarns: 1500 dtex multifilament yarn (made by Toray Monofilament Co., Ltd., product number: 1450T-68-3158)

TABLE 1 First base fabric (lower fabric) Second base fabric (upper fabric) Weave Weave Yarn used structure Yarn used structure Example 1 warp 1000 d yarn 84 f/5 cm warp double warp 1000 d yarn 40 f/5 cm warp double Without inserted yarns in the weft 1240 d yarn 80 f/5 cm weave weft 3/330 d yarn 40 f/5 cm weave vicinity of the seam loop part Example 2 warp 1000 d yarn 84 f/5 cm warp double warp 1000 d yarn 40 f/5 cm warp double With inserted yarns in the weft 1240 d yarn 80 f/5 cm weave weft 3/330 d yarn 40 f/5 cm weave vicinity of the seam loop part Comparative warp 1000 d yarn 84 f/5 cm warp double warp 1000 d yarn 40 f/5 cm warp double Without seam loops, Example 1 weft 1240 d yarn 80 f/5 cm weave weft 3/330 d yarn 40 f/5 cm weave slitting after joining Comparative warp 1000 d yarn 84 f/5 cm warp double warp Without second base fabric Example 2 weft 1240 d yarn 80 f/5 cm weave weft Comparative warp 1000 d yarn 84 f/5 cm warp double warp 1000 d yarn 84 f/5 cm warp double Same as first base fabric Example 3 weft 1240 d yarn 80 f/5 cm weave weft 1240 d yarn 80 f/5 cm weave

The evaluation tests hereinafter were conducted with the samples produced according to Examples 1, 2 and Comparative Examples 1 through 3. The evaluated items adopted in the present invention were the time until loosening of the second base fabric (upper fabric) occurred, the marking properties, the amount of lost fibers, the time required for the seaming process. The results are shown in Table 2.

Time Until Loosening of the Second Fabric (Upper Fabric) Occurred

The time until loosening occurred was measured by a high speed—high pressure papermaking test. The test conditions were as follows, papermaking speed: 1000 m/min, applied pressure: 100 kg/cm, HPS (high pressure shower): 15 kg/cm².

Marking Properties

The marking properties were evaluated by marking test using the device according to FIG. 6. In the test, felt, carbon paper, paper, batt were superposed and pressed by rolls (applied pressure: 30 kg/cm). The batt was added by 100 gsm (gram per square meter). The value of 1 part of 1000 of the batt weight was taken as marking index by which it was confirmed by visual observation that a base fabric marking was not transferred to the paper. The smaller the marking index the better the marking properties.

Amount of Lost Fibers

Evaluation was made by wear test according to Japanese Industrial Standard (JIS II) using the device of FIG. 7. The test conditions were as follows: The amount of worn fibers was measured by electronic scales after 400 slides at a frequency of 30 slides per minute. Sliding distance: 100 mm, wear terminal area: 20×20 mm, applied weight of wear terminal: 500 g, and sandpaper with a grit of 320 was used.

Seaming Time

The time required for seaming 1 m on a flat surface was evaluated.

TABLE 2 Evaluated items Time until loosening Mark- Amount of the second base ing of lost Seaming fabric (upper fabric) index fibers time Example 1 No loosening after 1000 0.6 60 mg 60 s/m hours Example 2 No loosening after 1000 0.5 60 mg 60 s/m hours Comparative Loosening after 300 0.6 70 mg 60 s/m Example 1 hours Comparative . . . 1.2 160 mg  60 s/m Example 2 Comparative No loosening after 1000 1.2 80 mg 150 s/m  Example 3 hours

The results of the evaluation tests, as shown in Table 2, demonstrate that, in Examples 1 and 2, there was no loosening of the second base fabric, or only after a very long period of time. The marking index was also small and the marking properties were good. The loss of fibers was small and there was a good resistance to fiber loss. Further, the seaming time was short, whereby a reduction of the time for installing onto the papermaking machine can be expected.

INDUSTRIAL APPLICABILITY

According to the present invention it is possible to obtain, even when a base fabric of a multilayer structure is used, a single seam felt for excellent surface smoothness of the wet paper, having good batt adhesion, and wherein, at the seam part of the stacked base fabric, the warp yarns do not fray and the weft yarns do not come loose.

This felt is particularly useful, even when using base fabrics of a thick and hard multilayer structure that have come into use as a result of the increase in operating speed, to increase wear resistance and dewatering capability during high speed operation, to obtain excellent surface smoothness of the wet paper surface and durability, and to facilitate the installing operations. 

1. Seamed papermaking press felt comprising a woven base material having seam loops at both ends and a batt layer, wherein said base material comprises a first base fabric having seam loops at both ends which is joined into an endless form by passing a pintle wire through said seam loops and one or more second base fabric(s) having seam loops at both ends, through which a pintle wire is not passed, which is (are) stacked onto said first base fabric, said batt layer, which is disposed at least on the wet paper side of said base material and is entangled with said base material, is cut in the widthwise direction in the vicinity of the seam loop part of said second base fabric.
 2. Seamed papermaking press felt according to claim 1, wherein the weight per area unit of the second base fabric is lower than the weight per area unit of the first base fabric.
 3. Seamed papermaking press felt according to claim 1, wherein the opening formed by the seam loops of the second base fabric is smaller than the opening formed by the seam loops of the first base fabric.
 4. Seamed papermaking press felt according to claim 1, wherein the loop length and loop height of the seam loops of the second basic fabric are respectively smaller than the loop length and loop height of the first base fabric.
 5. Seamed papermaking press felt according to claim 1, wherein, in the vicinity of the seam loop part of the second base fabric, yarns are further disposed to reduce the opening formed by the seam loop of the second base fabric.
 6. Seamed papermaking press felt according to claim 5, wherein the yarns are multi-filaments, bulky yarns or spun yarns.
 7. A kit comprising a seamed papermaking press felt, which comprises a woven base material having seam loops at both ends and a batt layer, and only one pintle wire to be passed through the seam loops, wherein said base material comprises a first base fabric having seam loops at both ends and one or more second base fabric(s) having seam loops at both ends which is (are) stacked onto said first base fabric, said batt layer, which is attached by entanglement at least to the wet paper side of said base material, is cut in the widthwise direction at the seam loop part of said second base fabric or in the vicinity thereof, said pintle wire joins said first base fabric into an endless form on the papermaking machine by being passed through the seam loops of said first base fabric.
 8. A method for producing a seamed papermaking press felt comprising a woven base material having seam loops at both ends and a batt layer, comprising a process for making said base material by stacking one or more second base fabric(s) having seam loops at both ends onto a first base fabric having seam loops at both ends, a process for making endless forms by joining the seam loops of one end of said first base fabric with the seam loops of the other end via a pintle wire and by joining the seam loops of one end of said second base fabric with the seam loops of the other end via a pintle wire, a process for entangling a batt layer with said base material by disposing it on the wet paper side of said base material which comprises said first base fabric and said second base fabric which have been made into endless forms, a process for making open-ended forms of said first base fabric and said second base fabric by withdrawing the pintle wires from the seam loops of both said first base fabric and said second base fabric, a process for making an open-ended felt by cutting said batt layer in the widthwise direction at the seam loop part of said second base fabric or in the vicinity thereof, and a process for making an endless form on the papermaking machine by re-inserting a pintle wire only into said first base fabric.
 9. A method for producing a seamed papermaking press felt according to claim 8, further comprising a process for weaving yarns in the vicinity of the seam loop part of said second base fabric, when said second base fabric is woven, to reduce the opening formed by the seam loops of said second base fabric.
 10. A method for producing a seamed papermaking press felt according to claim 8, further comprising a process for inserting yarns in the vicinity of the seam loop part of said second base fabric, after weaving the second base fabric and before entangling the batt part with the base material, to reduce the opening formed by the seam loops of said second base fabric. 